Therm-Rigid-Ave

Supported Applications

The ACI Thermistor Rigid Averaging Sensors are designed for use with electronic controllers in commercial heating and cooling building management systems. These sensors provide a better average temperature reading over the length of a duct compared to single-point sensing elements by utilizing four evenly spaced thermistor points or continuous platinum sensing. Documented applications include Air Handlers, Roof Top Units, Mixed Air/Discharge/Supply/Return Air Temperature Monitoring, Data Centers, and Hospitals.

Operating Conditions & Performance

The series features a 0.250" (6.35 mm) diameter probe constructed from 304 Stainless Steel with hermetically sealed elements to prevent moisture intrusion. Operating humidity is rated for 10 to 95% RH, non-condensing. Storage temperature ranges are documented as -40 to 80 °C (-40 to 185 °F) in the manual and -40 to 85°C (-40 to 185°F) in the data sheet.

Performance specifications vary by sensor element type:

• Thermistor Accuracy (0-70 °C / 32-158 °F): A/1.8K Series is ±/− 0.5 °C @ 25 °C (77 °F) and (±/−1.0 °C) (±/−1.8 °F); A/10K-E1 Series is ±/− 0.3 °C (±/− 0.54 °F); All Else are ±/− 0.2 °C (±/− 0.36 °F).
• Platinum Accuracy: Class A tolerance formula: +/− °C = (0.15 °C + (0.002 * |t|)) where |t| is the absolute value of Temperature above or below 0 °C in °C.
• Balco Accuracy (@ 21.1 °C / 70 °F): ±/− 1%.
• Nickel Accuracy: Ranges from ±/− 1.52 °C (+/− 2.73 °F) @ -40 °C (-40 °F) to ±/− 1.25 °C (2.25 °F) @ 121 °C (250 °F).
• Response Time: 10 Seconds nominal.

Enclosure temperature ranges depend on the selected housing material: Galvanized Steel (-40 to 115°C / -40 to 239°F), ABS Plastic (-30 to 90°C / -22 to 194°F), Aluminum (-40 to 115°C / -40 to 239°F), and Polystyrene Plastic (-40 to 70°C / -40 to 158°F).

Configuration Options

The series supports multiple sensor outputs, probe lengths, enclosure types, and optional certifications. Selection is configured via the model number structure: A/ [Sensor Series] - RA - [Probe Length] - [Enclosure] - [NIST].

Sensor Elements & Outputs

Available thermistor nominal outputs at 25 °C (77 °F) include:

• A/1.8K: 1.8 KΩ (Red/Yellow)
• A/3K: 3 KΩ (White/Brown)
• A/AN (Type III): 10 KΩ (White/White)
• A/AN-BC: 5.238 KΩ (White/Yellow)
• A/CP (Type II): 10 KΩ (White/Green)
• A/CSI: 10 KΩ (Green/Yellow)
• A/10K5 / A/10KS: 10 KΩ (White/Blue)
• A/10K-E1: 10 KΩ (Gray/Orange)
• A/20K: 20 KΩ (Brown/Blue)
• A/50K / A/50KS: 50 KΩ (Brown/Yellow)
• A/100K5 / A/100KS: 100 KΩ (Black/Yellow)

Platinum, Balco, and Nickel sensor options are also available with specific nominal outputs at defined temperatures.

Probe Lengths & Enclosures

• Probe Length: 12", 18", 24", 36", or 48". Standard lead length is 12" (30.5cm) with 22 AWG Etched Teflon colored leads.
• -GD Enclosure: Galvanized Steel, NEMA 1 (IP10).
• -PB Enclosure: ABS Plastic, UL94-HB, Plenum Rated.
• -BB Enclosure: Aluminum, NEMA 3R (IP 14), Bell Box style.
• -4X Enclosure: Polystyrene Plastic, UL94-V2, NEMA 4X (IP 66).

Certifications & Options

The series carries CE and RoHS2 approvals; the data sheet also lists WEEE. An optional NIST Certificate is available for specific configurations.

Key Product Differences

Variants differ primarily by sensor element type (Thermistor, Platinum, Balco, Nickel), probe length, and enclosure rating. The -PB Plastic Box Enclosure is Plenum Rated with a UL94-HB flammability rating, while the -GD Galvanized Enclosure provides NEMA 1 protection. The -BB Bell Box offers Aluminum construction with NEMA 3R (IP 14) ratings, and the -4X option utilizes Polystyrene Plastic for NEMA 4X (IP 66) weatherproofing.

Lead wire colors are specific to each sensor series to differentiate types. For example, A/AN-BC uses White/Yellow leads while A/CP uses White/Green. The manual notes that the sensors feature an integrated foam pad made of Neoprene/EPDM/SBR Polymer (UL94-HBF; FMVSS-302; MIL-R-6130C) to seal the duct and dampen vibrations.